This application claims the priority of Austrian utility model application GM 443/2002, filed Jul. 4, 2002, the subject matter of which is incorporated herein by reference.
The present invention relates, in general, to a tamping machine.
A track maintenance machine of this type is provided for tamping ballast underneath ties of a railroad track, and generally includes a machine frame, extending in a longitudinal direction and supported for mobility on the track by two undercarriages, and a tamping unit and a track lifting unit.
U.S. Pat. No. 4,655,142 and U.S. Pat. No. 5,515,788 disclose a tamping machine, with a subframe being arranged between two undercarriages of the machine frame and supported for mobility on the track by a further, separate undercarriage. A frame support connects the subframe to the machine frame in a manner allowing displacement of the subframe in the longitudinal direction. The vertically adjustable tamping unit and track lifting unit are arranged on the subframe between the further undercarriage and the frame support.
Tamping machines of this type can travel continuously during working operations, whereby the machine frame, which represents a major part of the total mass of the machine, does not have to be stopped at each tie to be tamped and then accelerated again immediately thereafter. This intermittent advance movement is limited only to the subframe, connected to the machine frame, which carries the working units and is designed for displacement relative to the machine frame.
It would be desirable and advantageous to provide an improved tamping machine which allows a tamping of track curve sections in a reliable manner.
According to one aspect of the present invention, a tamping machine for tamping ties of a track includes a machine frame extending in a longitudinal direction and supported for mobility on the track by two undercarriages; a subframe arranged between the said undercarriages and supported for mobility on the track by a further undercarriage; a frame support connecting the subframe to the machine frame in a manner allowing displacement of the subframe in the longitudinal direction, the frame support being mounted on the machine frame for displacement perpendicularly to the longitudinal direction; a transverse drive connected to the frame support and linked to the machine frame; and a vertically adjustable tamping unit and a track lifting unit arranged on the subframe between the further undercarriage and the frame support.
A tamping machine having a frame support designed in this way is particularly suited for tamping units which are adapted for tamping several ties of the track simultaneously. Owing to the transverse displaceability of the subframe it is now possible to center the tamping unit with respect to the rail in an optimal manner even in track curves.